The invention relates to the field of beer dispensing and apparatus therefore and in particular relates to a process for stabilizing foam from draft beer as it is dispensed.
In the art of making beer, it is very important that the appearance of the beer in the glass be attractive to the user. While flavor is the aspect most talked about in beer, appearance is the first thing noticed by the customer and that makes it important. The shade and depth of color, the clarity, beading, type of head foam, the foam retention, and the foam cling, all contribute to making the initial impression. It is desirable that the foam atop a glass of beer dispensed from a tap be smooth, creamy, be relatively stable and have an attractive taste. The incorporation of air or nitrogen into beer as it is dispensed at the tap spout gives a head of very fine bubbles with excellent stability and a creamy slightly sweet desirable taste.
The type of malt beverage which heretofore has attracted the most attention in connection with a stable creamy head is Irish stout. The dispensing of stout so as to achieve this desirable head has passed through numerous evolutionary stages. Originally the stout was krausened by the addition of fresh wort containing yeast, so that the stout developed about 30 to 35 psi pressure in the cask and when dispensed, issued as a fine smooth cream. As the cask was used it tended to become flat, so that the stout then was blended and served as a mixture of flat stout with a creamy head from a new high conditioned cask.
Later, a device known as a "Beamish Quick-One Server" was used, in which the conditioned stout was poured into a serving flask having a tap at the bottom, so that a glass was poured substantially full from the tap and then a creamy head poured from the top of the server.
Later, a dispensing procedure known as "B.D." or "bottling draught" was used. In this procedure, the pub owner utilized two casks of stout, one filled with a higher conditioned stout and one with a flat stout or "B.D." stout. A charge was drawn from the conditioned cask and the remainder of the glass filled with "B.D." stout.
There is a Scottish procedure which utilized a top pressure of air on a cask, but this sometimes resulted in differences in taste of the beverage from the cask due to oxidation effects.
Guinness utilizes a keg having a head of pressurized nitrogen or air to produce the desired foam and then utilizes a degasing system to provide flat beer for topping of the glass after the foam has been poured.
Beamish and Crawford has utilized a system of dispensing stout in which a low pressure keg having a special dispensing tap with a spherical ball mounted thereon is used. A portion of the stout is routed to the ball and pressurized with a mixture of nitrogen and CO.sub.2, so that manipulation of the dispensing valve allows for production of foam from the spherical head and subsequent filling with flat stout from the keg.
Presently a procedure is used whereby the beer is saturated with nitrogen at the plant prior to kegging. Foam is produced by releasing the beer through a small orifice in the tap and the remainder of the glass is filled with flat beer by bypassing the orifice. This too is caused by manipulation of the dispensing valve in the tap.
The foregoing described procedures are not totally satisfactory and, if nitrogen is used, an additional expense is involved. Also, several of the processes require the use of high pressure kegs, which, in turn, necessitates heavier duty installation in the pub.
It also is the general practice and custom in the brewing industry to exclude all possible air from contact with beer because of the known oxidizing effect of air on beer. Oxygen, when in contact with beer for periods of time tends to cause off flavors, etc. Accordingly, the incorporation of air into beer is contrary to present practices, but when added immediately prior to the beer entering the glass, the known deleterious effects are avoided.
Accordingly, it is an object of the present invention to provide a relatively inexpensive procedure for processing a foamed malt beverage which has stability in the foam. A further object is to provide an apparatus which can be utilized for dispensing both flat beer and foamed beer having a high degree of stability to the foam.
We have found that, using a Venturi effect, we are able to incorporate air or nitrogen in substantial amounts into the beer as it leaves the tap and prior to its entering the glass of the user. We have found that by dividing the stream of beer from the tap into a series of smaller streams of higher velocity, drawing air into the streams, and then creating turbulence in the stream so as to mix the air therein, we can create a beer foam comprised of bubbles of very small diameter which is extremely stable over a period of time. By combining this type nozzle with a conventional nozzle, we are able to draw a glass of beer having a head of a smooth, creamy foam which is stable and long lasting.
These and other objects and advantages will become apparent in the drawings and description hereinafter set forth.